Negative reactive circuitry



March 29, 1966 G. c. SZIKLAI 3,243,739

NEGATIVE REACTIVE CIRCUITRY Filed Oct. 20. 1960 Fig. l

WITNESSES INVENTOR George c. Sziklui two terminals.

United States Patent 3,243,739 NEGATIVE REACTIVE CIRCUITRY George C.Sziklai, Carnegie, Pa., assignor to Westinghouse Electric Corporation,East Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 20, 1960,Ser. No. 63,866 3 Claims. (Cl. 333-80) The present invention relatesgenerally to negative reactance circuitry and more particularly tonegative reactance circuits utilizing negative and positive resistancesand a reactance element.

It is desirable to product negative reactances in convenient form formolecular electronic blocks or other electronic systems designs. In suchmolecular blocks, capacitance is readily obtained. The present inventionallows a molecular equivalent of an inductance to be formed by means ofa capacitance region. The present invention also provides inductancewithout a magnetic field for conventional electronic systems designs.

An object of the present invention is to provide a two terminal negativereactance circuit.

Another object of the present invention is to provide a negativereactance circuit capable of compensating for positive reactance withina network.

Another object of the present invention is to provide a network forinverting both the sense and frequency dependence of a preselectedreactance.

Further objects and advantages of the present invention will be readilyapparent from the following detailed description taken in conjunctionwith the drawing in which:

FIGURE 1 is a characteristic curve of the device employed in the presentinvention;

FIG. 2 is a schematic diagram of an illustrative embodiment of thepresent invention;

FIG. 3 is a schematic diagram of an alternate embodiment of the presentinvention;

FIG. 4 is a schematic diagram of an alternate embodiment of the presentinvention shown in FIG. 2;

FIG. 5 is a schematic diagram of an alternate embodiment of the presentinvention shown in FIG. 3;

FIG. 6 is a schematic diagram of another alternate embodiment of thepresent invention; and

FIGS. 7 and 8 are schematic diagrams of illustrative embodiments of thepresent invention in a network.

The present invention utilizes the negative resistance provided by atunnel junction or by any other electronic means to create a twoterminal negative or complementary reactance. FIG. 1 shows thecharacteristic curve 2 of a tunnel diode. The tunnel diode provides adynamic negative resistance over a limited range of its characteristicsin the form of a single device having only The tunnel diode, due to itsnegative resistance, has been found to be useful in amplifying and inswitching circuits. It has been both postulated and demonstrated thatthe tunnel diode is useful at high frequencies and high temperaturesbecause the negative resistance portion of its characteristic curve isobtained by means of majority carrier conduction. The tunnel diodes usedin accordance with the present invention have been designated as H toindicate the dynamic negative resistance provided by these diodes. It isto be understood that the tunnel diodes have a voltage thereacross ofsuflicient magnitude to cause them to be biased into the negative regionof their characteristic curve as shown in FIG. 1.

FIG. 2 is a schematic diagram of a negative inductive reactance inaccordance with the present invention. The two terminal negativeinductive reactance comprises a capacitance C, a positive resistance R,and two negative resistances H; A negative reactance I is connected in aparallel circuit combination with a posi- "ice tive capacitance C. Apositive resistance R is connected in a series circuit combination withthe parallel circuit combination. The series circuit combination isconnected to the terminals A and B of the negative induc tive reactancecircuit. A second negative resistance fl is connected across the seriescircuit combination and also connects the terminals A and B.

It can be seen that the impedance Z across the terminals A to B can berepresented by the following equation:

T"' a 1) PC which, when factored out, takes a more simplified form:

H +pCH RHR (2) pC'H 2fl-pCH+R The symbol p may be representive of either'w or an operator d/dt.

Setting the negative resistance I equal to the positive resistance R,the impedance across the terminals A,

B is in the form:

AB p 2 from whence it can be seen that the actual equivalent inductancevalue has a magnitude CR If the symbol p is representative of iw or anoperator d/dt, it can be seen that the impedance of the circuit shown inFIG. 2 is:

Z -jwCR (4) and the voltage E is:

Z '2 EAB C' R Thus, it can be seen that the arrangement shown in FIG. 2appears to be a short circuit at direct current or extremely lowfrequencies while it appears to be an open circuit of extremely highfrequencies. The circuit as shown has application as a choke to providea direct current connection by an insulation for high frequency signals.

An alternate embodiment of a two terminal negative inductive reactancecircuit is shown in FIG. 3. A positive resistance element R and acapacitance element C are connected in a series circuit combination.ative resistance element .Fl is connected in parallel circuitrelationship with the series circuit combination. A second positiveresistance element R is connected in series circuit relationship withthe parallel circuit, all across the terminals A, B of the negativeinductive reactance circuit.

It can be shown that impedance Z across the terminals A to B shown inFIG. 3 can be represented as follows:

If, once again, the negative resistance element H is made equal inmagnitude to the positive resistance element R,

A neg FIGS. 4 and show counterparts of the circuits il lustrated inFIGS. 2 and 3, respectively. Each circuit illustrates a two terminalnegative capacitive reactance circuit wherein like elements aredesignated with identical reference characters used in the precedingfigures. An inductance L is inserted in place of the capacitance C.Accordingly, the impedance Z across the terminals A to B in FIG. 4 canbe represented as follows:

a -2 Ln-aR+ LR By making the magnitude of the negative resistanceelements I each substantially equal to the magnitude of the positiveresistance element R ZAB- 5 (11) If the symbol p is representative of jwor the operator d/dt it can be seen that the impedance of the circuitshown in FIG. 4- is:

1 ZAP T/ra and the voltage E is:

R E B='f/ Zdt Referring to FIG. 5, it can be seen that the impedanceacross the terminals A, B may be represented 1 AB= 'T'j+ R +jwL H whichmaybe simplified to HR HJwL 5) Setting the negative resistance fl to beequal in magnitude to the positive resistance R,

2 AB- jwL The Equations 12 and 16 demonstrate that the circuits shown inFIGS. 4 and 5 provide a negative capacitance across the terminals A, Bwith an equivalent capacitance value of L/R The circuits shown in FIGS.4 and 5 appear to be an open circuit at extremely low frequencies and ashort circuit at extremely high frequencies.

Another configuration consisting of a reactance with two negativeresistances -H and one positive resistance R is shown in FIG. 6 wherethe same inversion, both in sign and frequency dependence, is obtainedas in the previous figures. The reactance has been simply indicated asjX with the like elements used in the previous figures designated withidentical reference characters. It can be shown that the impedance Z ofthe circuit illustrated in FIG. 6 takes the form ZAB' An importantapplication of the circuits shown in FIG. 4 or 5 is the removal ofincidental, undesired positive capacitance efiects. Such incidental,positive capacitances limit the bandwidth in the upper frequencyoperations of amplifiers as well as imposing serious limitations on theupper frequencies of oscillators. As shown in FIG. 7, assume anundesirable positive capacitance C across the terminals A, B. If anegative capacitance, O such as obtained from the two terminal negativecapacitance circuit shown in FIG. 4, is connected across the undesirablecapacitance C the two conductances are additive; and if the capacitanceC is equivalent in magnitude to L/R the overall conductance is going tobe zero. The impedance of the combination shown in FIG. 7 is going to beinfinite at all frequencies. Thus, the negative capacitance -O willprovide an elimination or substantial reduction of the unwantedcapacitances in a circuit.

If an undesirable inductance is to be cancelled, as in FIG. 8, anegative inductance such as shown in FIG. 3 may be used. Assuming anundesirable inductance of magnitude jwL in series with a load resistanceR in a load circuit, the negative inductive reactance --jwCR may beadjusted to have a magnitude CR equal to L. Since the load resistance Ris in series circuit relationship with the negative inductive reactance,the positive resistance R having one side connected to the terminal Amay be reduced in magnitude so that the sum of the positive resistor Rand the load resistance R is equal to the negative resistance H. Thus,if an undesirable inductance is placed in series circuit with a negativeinductive reactance, as provided by the circuit shown in FIG. 3, thecurrent in the series circuit will level off until the negativeresistance H ceases to be a pure negative resistance. The usual fasterattenuation with increases in frequency is thereby avoided.

While the present invention has been described with a degree ofparticularity for the purposes of illustration, it is to be understoodthat all equivalents, modifications, and alterations within the spiritand scope of the present invention are meant to 'be included. While thecircuits shown have been illustrated as lumped component circuits, it isto be understood that the circuits described may be obtained in a singlematerial by various arrangements of junctions. In other words, twotunnel junctions may be obtained on a single semiconductor slab; aninverse biased junction may provide the capacitance, and the resistancemay be obtained through the inherent resistive behavior of thesemiconductor. A lumped positive inductance may be obtained from certainforward biased time delay junctions. Not only does the present inventionhave application in molecular electronic blocks but in other electronicsystems designed as well.

I claim as my invention:

1. An inversion circuit, both in sense and frequency dependence,comprising, in combination: a parallel circuit combination of a negativeresistance element and a reactance element of preselected sense andfrequency dependence; a series circuit combination of a positiveresistance element and said parallel circuit combination; a

second negative resistance element connected across said seriescombination; the magnitude of the negative resistance elements eachbeing substantially equal to the magnitude of the positive resistanceelement.

2. A negative inductance circuit comprising, in combination: a parallelcircuit combination of a negative resistance element and a capacitanceelement; a series circuit combination of a positive resistance elementand said parallel circuit combination; a second negative resistanceelement connected across said series circuit combination; the magnitudeof the negative resistance elements each being substantially equal tothe magnitude of the positive resistance element.

3. A negative capacitance circuit comprising, in combination: a parallelcircuit combination of a negative resistance element and an inductanceelement; a series circuit combination of a positive resistance elementand said parallel circuit combination; a second negative resistanceelement connected across said series circuit combination; the magnitudeof the negative resistance elements each 5 being substantially equal tothe magnitude of the positive resistance element.

References Cited by the Examiner UNITED STATES PATENTS 4/1957 Linvill333-80 7/1957 Towner 333-80 IRE Proceedings, July 1959, pp. 1268, 1269.Schultz: Amplifier Design, May 27, 1960, Electronics, pp. 110-112.

6 FOREIGN PATENTS 278.036 9/1927 Great Britain.

OTHER REFERENCES 0 Bartlett.

HERMAN KARL SAALBACH, Primary Examiner.

BENNETT G. MILLER, Examiner.

S-omrners: Tunnel Diodes, Preceedings of IRE, July 15 A. J. ENGLERT, W.K. TAYLOR, Assistant Examiners.

1. AN INVERSION CIRCUIT, BOTH IN SENSE AND FREQUENCY DEPENDENCE,COMPRISING, IN COMBINATION: A PARALLEL CIRCUIT COMBINATION OF A NEGATIVERESISTANCE ELEMENT AND A REACTANCE ELEMENT OF PRESELECTED SENSE ANDFREQUENCY DEPENDENCE; A SERIES CIRCUIT COMBINATION OF A POSITIVERESISTANCE ELEMENT AND SAID PARALLEL CIRCUIT COMBINATION; A SECONDNEGATIVE RESISTANCE ELEMENT CONNECTED ACROSS SAID SERIES COMBINATION;THE MAGNITUDE OF THE NEGATIVE RESISTANCE ELEMENT EACH BEINGSUBSTANTIALLY EQUAL TO THE MAGNITUDE OF THE POSITIVE RESISTANCE ELEMENT.